*** MERGE WITH 4.07 ***

* Fix the ambiguity check in TcMonotype.lhs so that
  it is not carried out for types read from interface 
  files.  Some workers may get ambiguous types but that
  does not matter, and should not make compilation fail.
  More detail in the comments with TcMonoType.tc_type_kind
  (the HsForAll case)

* Don't create specialisations for type applications 
  where there's a matching rule.  The rule should
  clearly take precedence.  (Bug reported by Sven.)
  I havn't tested this fix.

* Run the occurrence analyser after tidyCore, so that
  occurrence info (notably dead-var info) is correct
  for the code generators.  This should fix Erik's problem,
  but again I've not tested the fix.  The extra call 
  is in Main.lhs

* Fix CoreToStg so that it can handle an StgLam in mkStgCase.
  This only shows up in a wierd case, documented in 
  CoreToStg.mkStgCase